Rotifer size distribution changes during transient phases in open cultures

Abstract

In laboratory studies, rotifers (Brachionus calyciflorus) were monitored under well-defined environmental conditions at different supply rates of a unicellular algal food (Chlorella vulgaris). Rotifer size frequency distributions are described for conditions of steady-state growth, exponential increase, and starvation. Temporal fluctuations in size-age structure are described for cultures during transient conditions during the approach to a steady state and following step changes in food supply rate. The size structures of the populations displayed definite and reproducible shifts among typical patterns during transient conditions, reflecting the physiological and other dynamic processes that underlay the population dynamics. Size structure probably is a key variable that should be included in models for predicting growth dynamics during transient growth conditions.